Before any of the bust-sayers come out, it's pretty clear to tell that this season is above average at this point. According to the NHC, the seventh storm forms on September 16th, based on the average from 1966 to 2009. That means we're over a month ahead. Put another way, the typical season in that same period has three storms at this point. If one goes from 1995 to 2010 (the active period), seasons have averaged 3.75 storms by this point, of which only 1995 and 2005 were ahead of this point. In fact, this season is the 4th fastest to reach the 7th TS, behind 2005, 1936, and 1995, but amazingly ahead of 1933 and 1887.
It is true that it's slightly unusual that there have only been one hurricane at this point. The average date (1996-2009) for the first hurricane is August 10th. However, nine out of sixteen seasons (56%) had a hurricane before this day, which isn't that outstanding. In fact, two important seasons that didn't have a hurricane at this point include 1998 and 1999, which each only had one storm at this point; they both went onto having monsters such as Georges and Mitch (98) and Floyd and Lenny (99).
Perhaps one of the more unusual aspects of this season is that four of the seven storms formed above 25º North. To put that into perspective, the last entire season to accomplish that was 2007, which had five such storms. One unusual part about 2007 is that it had a high ratio of relatively weak and short-lived storms (which does sound similar to this year). Going back to, 2002 had three storms form above 25º North by this point of the year, while several others had two. 2002 was another season with a high ratio of weak and short-lived storms. The difference between 2007 and 2002 however (aside from 2007 having two landfalling C5 hurricanes) was that 2002 was an El Niño and 2007 was a La Niña.
Some climatology for this year
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Hurricanehink
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Some climatology for this year
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Re: Some climatology for this year
1998 and 1999 season were horrible and deadly. 1998 was an outlier in lives lost from Mitch and Georges. 1998 is the deadliest besides 1780 and 1900.
Last edited by Ptarmigan on Mon Aug 15, 2011 12:11 am, edited 1 time in total.
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AJC3
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It really depends on what you consider an "above average" season. I think the most objective metric for seasonal activity would be ACE, and in spite of 7 NS in the ATLC basin, the basinwide ACE is a pretty woeful 10.6 compared to the seasonal to-date normal of about 14. It tells you just how weak and relatively short-lived the seven NS thus far have been.
So, since the ATLC basin usually has fewer NS, but a higher ACE by this point in the season, I think it might be more accurate to say we have had an "above normal" number of "abnormally weak" tropical cyclones.
So, since the ATLC basin usually has fewer NS, but a higher ACE by this point in the season, I think it might be more accurate to say we have had an "above normal" number of "abnormally weak" tropical cyclones.
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dwsqos2
Re: Some climatology for this year
Yeah, while I think large scale factors favor an active season, it is entirely objective to call the early portion of the 2011 season pathetic.
One storm, Emily, has formed in the MDR.
As Hurricanehink noted, four storms formed north of 25N and had non-tropical origins: Bret, Cindy, Franklin, and Gert. Usually that indicates upper troughs floating around where hurricane lovers don't exactly want to see them.
The ACE is as already noted previously below the climatological mean. ACE takes into account strength and longevity of systems, something that raw storm counts don't. I can't say I really care about Nana 2008, Jerry 2007, Franklin 2011, and Tokage 2011. But I don't blow a gasket when storms like these are classified unlike others because I recognized that there is a metric that accurately quantifies their contribution to total seasonal activity. A raw storm count would suggest that Nana of 2008 comprised 1/16 of the season; however, an ACE total would show that Nana generated less than 1/100 of the season's activity.
Also, I suspect that the IKE for the season is really low as well considering that all of 2011s storms with the exception of Arlene have been tiny.
Really, I think my annoyance with the season stems from all the blather about an early active season from a number a relatively reputable sources. It would take a very generous reading of seasonal activity to argue that the activity of the last two and a half months constitutes above average activity. 1996, 2003, 2008, 2005, 1995, 1989, and 1979 are the seasons that come to mind when I think of active early seasons. This one doesn't and probably never will.
Of course that doesn't mean that 2011 by ACE or NTSC definition won't be quite active. It's just that the early season hasn't been.
One storm, Emily, has formed in the MDR.
As Hurricanehink noted, four storms formed north of 25N and had non-tropical origins: Bret, Cindy, Franklin, and Gert. Usually that indicates upper troughs floating around where hurricane lovers don't exactly want to see them.
The ACE is as already noted previously below the climatological mean. ACE takes into account strength and longevity of systems, something that raw storm counts don't. I can't say I really care about Nana 2008, Jerry 2007, Franklin 2011, and Tokage 2011. But I don't blow a gasket when storms like these are classified unlike others because I recognized that there is a metric that accurately quantifies their contribution to total seasonal activity. A raw storm count would suggest that Nana of 2008 comprised 1/16 of the season; however, an ACE total would show that Nana generated less than 1/100 of the season's activity.
Also, I suspect that the IKE for the season is really low as well considering that all of 2011s storms with the exception of Arlene have been tiny.
Really, I think my annoyance with the season stems from all the blather about an early active season from a number a relatively reputable sources. It would take a very generous reading of seasonal activity to argue that the activity of the last two and a half months constitutes above average activity. 1996, 2003, 2008, 2005, 1995, 1989, and 1979 are the seasons that come to mind when I think of active early seasons. This one doesn't and probably never will.
Of course that doesn't mean that 2011 by ACE or NTSC definition won't be quite active. It's just that the early season hasn't been.
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